Unable to extract result from Gio.SimpleAsyncResult

[Elv13]

Hi,

I try to use GDbus with lgi but I have some issue. When I try to do a synchronous call it works fine (remove the 3 last arguments from the example below and use call_sync and it will work as expected). However, I cannot find a way to extract SimpleAsyncResult results. Most methods seems to be there but the only useful one. I was wondering if I missed something or it just required unimplemented and/or undocumented hacks to get the result.

Here is a semi working example:

local lgi  = require     'lgi'
local Gio  = lgi.require 'Gio'
local core = require     'lgi.core'
local GLib = lgi.require 'GLib'
local type,unpack = type,unpack
local bus = Gio.bus_get_sync(Gio.BusType.SYSTEM)


local ret,err = bus:call(
    "org.freedesktop.UPower",
    "/org/freedesktop/UPower",
    "org.freedesktop.UPower",
    "HibernateAllowed",
     nil,
     nil,
     Gio.DBusConnectionFlags.NONE,
    -1, -- Timeout
     nil, -- Cancellable
     function(conn,res)
         print("async",conn,Gio.SimpleAsyncResult.get_op_res_gpointer,res:get_op_res_gssize()) --Ok
         print("async",conn,Gio.SimpleAsyncResult.get_op_res_gpointer,res:set_op_res_gpointer()) --Fail
     end
)

local main_loop = GLib.MainLoop()
main_loop:run()

I failed to find a way to get tge boolean back. C examples use set_op_res_gpointer, but it doesn't seem to exist in LGI

Thanks

[pavouk]

Sorry that it took so long.

I don't think that you need or should use SImpleAsyncResult, because it is intended to use when implementing asynchronous API, not when you are using it. You should use appropriate _finish() method to retrieve call result. Following modification of your callback argument makes this work:

function(conn, res)
   local ret, err = bus:call_finish(res)
   print(ret, err)
end

Please check giostreams.lua sample distributed with lgi to see possible ways how to deal with Gio async API, particularly Gio.Async could be useful. Your example rewritten in Gio.Async looks like this:

   ... 

   Gio.Async.call(function()
      print(bus:async_call(
         'org.freedesktop.UPower',
          '/org/freedesktop/UPower',
          'org.freedesktop.UPower',
          'HibernateAllowed',
          nil,
          nil,
          'NONE',
          -1))
   end)()

   ...

See Gio.Async docs in https://github.com/pavouk/lgi/blob/master/docs/gio.md

I hope that this helps, feel free to reopen if you still have problems with it.